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. 2021 May 11;12:656516. doi: 10.3389/fphys.2021.656516

FIGURE 3.

FIGURE 3

At pacing cycle length (PCL) = 220 ms, cyclopiazonic acid (CPA) increased the magnitude of both action potential duration (APD) (A) and sarcoplasmic reticulum (SR) Ca2+ (B) alternans. Mean ± SD. N = 3 (*p < 0.05 vs. Baseline). (C,D) Example SR Ca2+ traces at a slower (C) and faster (D) PCL. High-dose CPA (10 μM) tended to decrease alternans magnitude at slower rates, while increasing alternans magnitude at faster rates. (E,F) Quantification of release (E) and load (F) alternans according to the equations indicated. Shaded bars in (C,D) show approximate measurements for calculations in (E,F). S, small; L, large; D, diastolic level. (G) Under all conditions, release alternans emerged at a longer PCL than load alternans. Mean ± SD. N = 3 (*p < 0.05 vs. corresponding threshold for release alternans).